So after your grandparents died, they left you all the important family keepsakes—photos of their children, your grandmother's wedding dress, your great-grandfather's army discharge papers, the manifest from the ship that brought your daddy's people over from Ulster, and that Bible that's been in your mama's family since 1889.

You were flattered that they trusted you will all those incredibly important things. You went to their old house and walked out to the garage where they kept their papers in that big whicker chest next to your granddad's band saw. You opened it and…

Oh! There is a heavy, earthy, nasty scent to everything. And when you pull out the first papers, you find they are dotted with little white spots of something or other. You pull out the Bible and it's spotted too. And your grandmother's wedding dress!

Mildew! Mildew is on everything!

You were able to save some of the keepsakes, but others are gone forever. And the Bible is ruined. All those memories! All those keepsakes! Gone.

How could this have been prevented? And how, you wonder, can you protect your papers so that when you pass them on to your grandchildren this won't happen again?

The answer: Silica gel.

Mildew is a living thing, of course. Specifically, it is a fungus. The Fungi Kingdom contains everything from mushrooms to mold to the nasty little microbes that cause athlete's foot.

People used to think that fungi were a kind of plant. They thought fungi were plants that had somehow lost the ability to produce their own food by combining sunlight with water and minerals (i.e., "photosynthesis"). Instead, a fungus lives by taking in nutrients from its environment. That's why it grows on paper, or in leaves, or on that piece of bread you left out on the counter for a couple days.

But, more recently, scientists have figured out that fungi aren't plants at all. In fact, they are more like primitive animals. When plants want to build solid structures inside themselves, they use a material called "cellulose," which is what makes up wood and paper. But, when fungi want to build solid structures, they use a substance called "chitin," which is the same thing a lobster's shell or an insect's exoskeleton is made of. And, when plants store food, they turn it into starch (what's in bread and potatoes). But, when fungi store food, they turn it into a chemical called "glycogen," which is what animals (and people) do too.

Most of the time, fungi and people get along just fine. They don't bother us and we don’t bother them.

In fact, we've actually got partnerships going with some fungi. Yeast is a fungus, so anytime you eat bread or have a beer, you're consuming something a fungus helped produce. And, of course, if you've ever had mushrooms on a pizza or in a salad, you've eaten a fungus. (Some people have even suggested that the Manna from Heaven mentioned in the Bible may have been some sort of fungi.)

But, there are a few kinds of fungus that we don't like. Some cause diseases, like athlete's foot and Candida, and others can cause serious damage to our food, property, and plants.

Unfortunately, mildew is one of the bad fungi. Some mildews can make plants sick. Others grow in paper, clothing, leather, and even in the walls of your house. That's why it showed up in your grandparents' records…and ruined so many of them.

What can you do about it? Well, Mildew, like most fungi, needs water (a lot of water) to grow. Take away the water and the mildew can't happen. And one way you do that is silica gel.

Silica gel is a "desiccant," a substance that sucks up water in its environment. In fact, it is one of the best desiccants ever discovered. That's why you find little packets of the stuff in shoeboxes and other purchases (sometimes even in food products). They help keep moisture from damaging your purchases.

You can get Silica gel packets easily and cheaply from companies like http://silicagelpackets.com/. A few dollars will buy you a whole bunch of gram or half-gram packets. (There are even Silica gel packets that change color when they've absorbed as much water as they can. These are called "indicating" packets. You just give them a glance and, if they've turned green, you know it is time to get new ones.)

And you can use them to safeguard your papers.

Obviously, you start by storing your papers, clothes, or whatever someplace that is usually cool and dry—not, in other words, in a wet basement or attic. Second, you can invest in some plastic storage bins that have a lid and snap shut. You can get them easily from any stationary supply or big box store.

Then, after you've put your items in the bins, drop in a few silica gel packets before you close them up. You don't need many, just a few for a small box or a half a dozen or so for a large bin. That way, when you close the lid, you'll know that those packets will be in there, scooping up any humidity they can find, and keeping your goods safe in the process.

Also, check on the bins every year or so. Open them up and look at the packets to see if they are saturated and need to be replaced. Or just get new packets annually. That way you can be sure that you've done everything you can to keep moisture and mildew at arm's length.

And once you've got mildew mastered, you can get on with important stuff. Like reading those stories of your family at Ellis Island or marveling at the beauty of your grandmother's wedding dress.

Oh, and then afterwards, maybe you should go out for a beer and a steak with mushroom sauce—just so fungi remembers who's boss.

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PHOTO ONE: Mildewed Book -- Caption: "Mildew is a fungus. It can destroy your most important papers and keepsakes. Silica Gel, though, gives you a chance to fight it."

The photo should be created as follows: "Photo by David Kennedy, released on Wikimedia under a Creative Commons license."